1. Field of the Invention
The present invention relates to a high-voltage oscillator, that is, an oscillator able to operate with supply voltages that can reach several hundreds of volts.
2. Discussion of the Related Art
An example of application of the present invention relates to supply systems intended to provide a regulated D.C. voltage. Among conventional solutions in this supply application, transformer systems, which have the disadvantage of being heavy, bulky, and expensive, and switched-mode converter type systems are known. Switched-mode power supplies have as remarkable disadvantages a power dissipation originating from the fact that the cut-off switch generally has an abrupt switching (MOS or IGBT transistor), and the absence of a voltage provided as soon as the circuit is started or connected. It is indeed generally necessary for an auxiliary power supply of a control circuit to provide a sufficient power to control the supply voltage cut-off switch.
An example of a power supply where a high-voltage oscillator is used relates to the field of compact fluorescent lamps (CFL). The fluorescent tube supply is generally obtained by means of an H-shaped half-bridge controlled either by a transformer, or by an integrated circuit oscillator. In this last case, a voltage reference problem for the control of the transistor of the upper bridge branch is posed, which requires use of a level shifter.
The present invention will be described hereafter in more specific relation with an application to a supply circuit. It should however be noted that it more generally applies in all fields where a high-voltage oscillator may be required. For example, these may be applications to induction power transfer, such as wireless battery chargers or induction hot plates.